FR2487610A1 - Off-hook condition detector for telephone - has leaf contact switch located in magnetic field of line coupling transformer signals indicating replacement of handset - Google Patents

Abstract

The appts. provided to detect the replacement of a telephone handset. The telephone lines (L1,2) are coupled to the terminal through a coupling transformer whose primary coil (P) is connected to the lines and whose secondary (S) connects with the terminal. A leaf contact switch, such as a reed switch (1L3), is located adjacent the primary. During use of the telephone, the primary current is too small to close the switch. When the telephone is replaced the normal primary current closes the switch, applying a signal to a unit (3) which is in the form ofa clock or the like. The system does not require the insertion of additional components on the subscribers line.

Description

Detection device for not hanging up a telephone set
The invention relates to a device for detecting the non-hanging up of a telephone set.

 In the case of the use of a data transmission terminal on a telephone line, the terminal is associated with a telephone set which is used to establish communications for the requesting terminal; this is the case of terminals allowing the use of a remote time-sharing database via the telephone network.

 The telephone set's handset must be hung up when communication is established between the terminal associated with it and a remote device with which it is connected, in order to eliminate any interference from the telephone set on the established call, and avoid '' occupy the line with the set when the communication with the database is cut.

 The object of the invention is to detect the non-hanging up of a telephone set by disrupting the established communication as little as possible and by not consuming energy on the telephone line.

 The subject of the invention is a device for detecting the non-hanging up of a telephone set associated with a terminal, characterized in that it comprises a switch constituted by two contacts, said switch being placed in the magnetic field of a transformer. coupling of the terminal to a subscriber line, the contacts being connected to a signaling device.

 According to another characteristic of the invention, the transformer has a magnetic circuit with a central chimney and the switch is a switch with flexible blades sealed under a glass bulb, said bulb being placed in the chimney.

 The invention will be described using an embodiment illustrated by the single appended figure which is a diagram of the detection device of the invention.

 A subscriber line, consisting of two wires L1, L2 is connected on the one hand to a telephone set P and on the other hand through a switch 4 to a primary winding 1 of a coupling transformer constituted by a magnetic circuit 2, the primary winding 1 and a secondary winding 3. The secondary winding 3 is connected to a terminal T. The magnetic circuit 2 of the transformer has a central chimney. Switch 4 is used to commission the terminal.

 A flexible reed switch, 'ILS, is inserted in the central chimney; the switch comprises two flexible blades of magnetic material, and the flexible blades are connected to a signaling device S associated with the terminal T. The signaling device signals the non-hanging up, by any appropriate visual and / or audible means, or even by command of a clear text on the terminal screen.

 The operation of the detection device is as follows.

 When the terminal is in service and the telephone set's handset is off the hook, the direct current in the primary winding 1 of the transformer connected to the subscriber line is abnormal, i.e. it is abnormally weak due to the presence of the telephone set in parallel with the terminal on the subscriber line.

 When the current in the primary winding 1 is normal, combined with the telephone set on hook and terminal in service, the magnetic field created by the direct current in the chimney is sufficient to control the closing of the flexible reed switch; this is no longer true when the telephone set is in the off-hook state, and the contacts of the flexible reed switch are no longer closed, which indicates that the handset of the telephone set has not hung up.

 The detection device of the invention has the advantage of not inserting additional components on the wires of the subscriber line, which limits the possibilities of disturbance and faults, and eliminates drops in line voltage and energy consumption that additional components necessarily introduce when they are connected to the subscriber line.

 Of course, the detection device of the invention operates regardless of the direction of the direct current in the subscriber line.

 The detection device of the invention can be used with any terminal associated with a telephone set, and in particular, but not exclusively, with a terminal allowing the consultation of a directory such as for example a telephone directory, or even of a schedule.

 The invention is in no way limited to the device described and shown, and it is possible, without departing from the invention, to replace any component with an equivalent component.

Claims (2)

1 / Device for detecting the hanging up of a telephone set associated with a terminal, characterized in that it comprises a switch constituted by two contacts, said switch being placed in the magnetic field of a transformer coupling the terminal to a line subscriber, the contacts being connected to a signaling device. 2 / Device according to claim 1, characterized in that the transformer has a magnetic circuit with central chimney, that the switch is of the type with flexible blades sealed under a glass bulb, and that said bulb is placed in the chimney.